Hard disk drives employ a technique called zoned bit recording (ZBR) for storing information on the disk media. ZBR is a technique where recording tracks are grouped into zones based on their distance from the center of the disk and each zone is assigned a number of sectors per track. In practice, the disk media characteristics differ from one data zone to another and each read head also has its unique response to the recorded data. In addition, no two disks are alike. As a result, the signal-to-noise ratio (SNR) of the signals read back from the head typically varies from zone to zone, head to head, and disk to disk. The SNR may also vary with temperature and other operational parameters. Therefore, the read channel is expected to be optimized for each disk, and for each zone and head.
In conventional disk drive systems, adaptive equalization techniques have been applied in order to take into account the variations between data zones, read heads, and disks. For example, during the test stage of manufacturing, the equalizer coefficients are trained or optimized based on known pseudo-random data recorded on the corresponding data zone. This process is repeated for each data zone and each head and the obtained equalizer coefficients are cached in RAM and stored at “a reserved area” on the disk or in a flash memory. During data detection, the microcontroller retrieves the equalizer coefficients for each data zone and head, and uploads them into the equalizer. In this way, the performance of the equalizer and channel detector can be optimized for each data zone and read head. However, up till now, the error correction codes (ECCs) such as the LDPC codes used for hard disk drives are fixed across the disk media. However, these fixed ECCs cannot take into account the variations in zones and disk heads.
Thus what is needed is a method for deriving error correction codes (ECCs) for data detection optimized for each zone and head, which can provide improved data recovery accuracy. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.